You can request your customers to provide their card details via a link through an email to automatically pay off their invoices using the Request Payment Method. This process is detailed below.
This option automatically enables the Auto Collection feature for all future invoices.
In order to collect a past invoice you can enable the Attempt payment collection when payment method is added option under Configure Chargebee > Billing rules.
Please note this will collect the most recent payment due and not paid invoice.
Hope this helps!